libmpv: mpv_render_context_create crashes if failed to get opengl function pointer

[lhc70000]

mpv version and platform

mpv 0.29.1
macOS 10.14.3

Reproduction steps

When using the render.h API, call mpv_render_context_create when OpenGL is unavailable or not ready. It can be reproduced by simply returning NULL in the function provided for get_proc_address.

#6249 and #6379 might be related.

Expected behavior

mpv_render_context_create should return the error code if cannot get the OpenGL entry point.

Actual behavior

mpv_render_context_create crashes (EXC_BAD_ACCESS) at:

mpv/video/out/vo_libmpv.c

Line 300 in e5c4164

ctx->renderer->fns->destroy(ctx->renderer);

Seems that the resource is freed twice (the first time at

mpv/video/out/vo_libmpv.c

Line 194 in e5c4164

ctx->renderer->fns->destroy(ctx->renderer);

), if err returned by ctx->renderer->fns->init is less than zero.

Log file

N/A

Sample files

N/A

[wnoun]

See #6540